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[Solved] Choosing a Fuse for 10kW Heater with 400V Power Supply: Understanding Phase Currents

wiesko42 19167 16
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Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
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  • #1 17935525
    wiesko42
    Level 8  
    Hello
    I need help selecting fuses for the heater.
    10kW heater, 400V power supply
    And so P=UxI | I=P/U | I=10000/400=25A
    And now I don't know whether 25A is the sum for the entire line (3x8.33A) or for a single phase?

    The second thing is that the heater consists of 3 heaters connected in a star pattern, which means that one heater has 3333W and a voltage of 230V, and as above
    I=3333W/230V=14.5A but with a 230V power supply and the entire system is 400V
    Maybe someone will help you choose.
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  • #2 17935555
    kortyleski
    Level 43  
    What type of heater is it? Because something about these powers doesn't suit me. Generally, you calculate the current for one star branch at a specific power and voltage of 230V. At the same time, it is a good idea to connect the center point of the star with N. During normal operation, it does not matter, but if one heater fails, the other two work normally.
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  • #3 17935562
    Pyzaczek
    Level 20  
    wiesko42 wrote:
    I need help selecting fuses for the heater.

    wiesko42 wrote:
    ...the heater consists of 3 heaters connected in a star pattern, hence it may result that one heater has 3333W and a voltage of 230V and as above
    I=3333W/230V=14.5A...

    No help needed, calculations OK
  • #4 17935673
    wiesko42
    Level 8  
    Ok, so 16A protection per phase. But then what current will be consumed by this heater system? 25A or maybe 14.5 x3 = 43.5A I don't understand here?
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  • #5 17935702
    Pyzaczek
    Level 20  
    I would give 20 A. Consumption 14.5 A from each phase.
  • Helpful post
    #6 17935781
    retrofood
    VIP Meritorious for electroda.pl  
    wiesko42 wrote:
    Ok, so 16A protection per phase. But then what current will be consumed by this heater system? 25A or maybe 14.5 x3 = 43.5A I don't understand here?

    Play around with this:
    Power and current calculator in three-phase systems

    Use cos φ = 1, If - current of one phase
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  • #7 17935861
    nuszek
    Level 30  
    14.5 A for each phase, but it should be noted that the power is given for a heated heater, when a cold heater is switched on, its resistance is lower and the current will be higher when switched on, and this must be taken into account when selecting the protection.
  • #8 17938395
    wiesko42
    Level 8  
    The view and available description are attached.
    I didn't expect that the current consumed by the heater would be so high 14.5x3=43.5A I don't understand now since the heater is powered by 400V then P=400Vx43.5A| P=17.4kW, not 10kW. I thought that the current would be of the order P=UxI| I= 10000W/400V| I=25A, I will not mention the calculations from the calculator provided in the thread where the value is 18A.
    Attachments:
  • #9 17938421
    kortyleski
    Level 43  
    The description is misleading. The heater is connected in a star, so the power supply for each branch of the star is 230V. And for this voltage you calculate the branch current. So 3300/230.
  • #10 17938533
    wiesko42
    Level 8  
    Ok, at this point I may have misled the forum users. The description of the product I bought does not indicate that it is star-connected. I cannot contact the distributor. When I have more information, I will post it here. Thank you for your help
  • #11 17938592
    kortyleski
    Level 43  
    Show me what the connection looks like under this white box.
  • #12 17938796
    Pyzaczek
    Level 20  
    If the heaters are connected in a star, the current consumption from each phase is 14.5 A, and if they are connected in a delta, the current consumption from each phase is approximately 8 A.
    That's what.
    Measure the resistance of one heater and everything will be clear.
  • #13 17938863
    nuszek
    Level 30  
    Pyzaczek wrote:
    If the heaters are connected in a star, the current consumption from each phase is 14.5 A, and if they are connected in a delta, the current consumption from each phase is approximately 8 A.
    That's what.

    What nonsense , 10 kW in a star is also 10 kW in a triangle, the current on each phase will be the same, i.e. 14.5 A.
    Approx. 8 And it will flow when two heaters burn out and only one of the triangle connections remains.
  • #14 17938886
    retrofood
    VIP Meritorious for electroda.pl  
    nuszek wrote:
    Pyzaczek wrote:
    If the heaters are connected in a star, the current consumption from each phase is 14.5 A, and if they are connected in a delta, the current consumption from each phase is approximately 8 A.
    That's what.

    What nonsense , 10 kW in a star is also 10 kW in a triangle, the current on each phase will be the same, i.e. 14.5 A.
    Approx. 8 And it will flow when two heaters burn out and only one of the triangle connections remains.

    If you guys used the right terms, there would be no disputes. In a star, phase current = current of 1 heater, but in a triangle the phase current is different from the current of 1 heater.
  • #15 17938995
    wiesko42
    Level 8  
    Resistance +/- 17.5 Ohm for one heater. The connection shows that it is a star. I don't understand why the markings are 3x400V and not 3x230V? As I understand it, from common N, each heater is connected to a single phase. G1-f1, G2-f2, G3-f3, so there is 230V per heater.

    Unless the heater is simply for 400V phase voltage and interphase voltage is 690V
    Attachments:
  • #16 17939038
    retrofood
    VIP Meritorious for electroda.pl  
    You have a clear star like a bull. Without a doubt.
  • #17 17946442
    wiesko42
    Level 8  
    The 3x400V marking is the manufacturer's marking. I still don't understand this marking for star connection. In any case, the heater is powered by 3X230V. The rest is as in the posts above. Greetings to forum members. Current flowing 3x 14.5A
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Topic summary

The discussion revolves around selecting appropriate fuses for a 10kW heater powered by a 400V supply. The user calculates the current as 25A for the entire system but is confused about whether this is the total or per phase. The heater consists of three units connected in a star configuration, leading to a phase current of approximately 14.5A per heater at 230V. Participants clarify that the current consumption from each phase is indeed 14.5A, and suggest using 16A or 20A fuses for protection, considering the inrush current when the heater is cold. The conversation highlights the importance of understanding the connection type (star vs. delta) and the implications for current calculations. The user later confirms the star connection and expresses confusion over the manufacturer's 3x400V marking, which is clarified as being standard for such configurations.
Summary generated by the language model.
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